Reservoir Life Expectancy in Relation to Climate and Land-Use Changes: Case Study of the Mangla Reservoir in Pakistan

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Citation

Sarwar, S. (2013). Reservoir Life Expectancy in Relation to Climate and Land-Use Changes: Case Study of the Mangla Reservoir in Pakistan (Thesis, Doctor of Philosophy (PhD)). University of Waikato, Hamilton, New Zealand. Retrieved from http://hdl.handle.net/10289/7761

Abstract

The dams and reservoirs are one of the largest sources to store surface water. The escalating water crisis in the new millennium has made it very important to preserve available water and in turn to preserve the storage capacity of dams and reservoirs. Dams and reservoirs lose their capacity due to sedimentation. Climate change and land-use changes have the potential to generate more sediment load hence accelerating this depleting process. An example is the Mangla Dam in Pakistan - the second largest dam in the country. Agriculture in the Punjab province, with almost 65% of the country’s population, is dependent on this dam. Due to sedimentation, the Mangla Reservoir has already lost 20% of its original storage capacity and an accelerated capacity loss is expected due to climate and land-use changes in the future.

The dams and reservoirs are one of the largest sources to store surface water. The escalating water crisis in the new millennium has made it very important to preserve available water and in turn to preserve the storage capacity of dams and reservoirs. Dams and reservoirs lose their capacity due to sedimentation. Climate change and land-use changes have the potential to generate more sediment load hence accelerating this depleting process. An example is the Mangla Dam in Pakistan - the second largest dam in the country. Agriculture in the Punjab province, with almost 65% of the country’s population, is dependent on this dam. Due to sedimentation, the Mangla Reservoir has already lost 20% of its original storage capacity and an accelerated capacity loss is expected due to climate and land-use changes in the future time will have compound effects on reservoir life. In addition to mean climate factors, climate change will have a more profound impact on climate variability, which will likely lead to a more intensified and frequent extreme rainfall events than is currently experienced. Rainfall is the main driving factor of river sediment load, especially extreme rainfall events, which can cause exceptionally high sediment load compared to normal rainfall events. Therefore impacts of climate change was investigated by transient climate change scenarios from 1980 to 2098 constructed through bias correction of General Circulation Models (GCM) daily simulation outputs for the observed weather stations in the catchment. Land-use change scenarios were generated for two broad conditions based on socio-economic data and physical factors influencing the land-use: (i) pro-agriculture scenario and (ii) pro-industrialization scenario.

The impact of climate and land-use changes on the reservoir life was then investigated by using various combinations of climate change scenarios and land-use change scenarios. The results show that both climate and land-use changes can have significant impacts on the Mangla basin sediment transported by the river to the dam reservoir; climate change has a large impact on the annual sediment load, monthly variation in the sediment load, and in turn the reservoir life. The superimposed effects of land-use on climate change can exacerbate or reduce such impacts. Land-use change has the potential to effectively reduce climate change impacts. Therefore various land-use management measures were further evaluated based on economic analysis as adaptation options to mitigate the climate change impacts.